Drafting ruler



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' DRAFTING RULER Filed Aug. 8, 195e 2 sheets-sheet 2 Fafo" ATTORNEYS.

Patented Dec. 5, 1939 UNITED'STATES PATENT OFFICE 2,182,028 DRAFTING RULER Charles Henry Little and Charles Hubbard Little, Cleveland Heights, Ohio Application August 8, 1936, Serial No. 95,002

The present invention relates to drafting dev vices or instruments used in drafting, and more particularly to a composite drafting ruler or scale 2 Claims.

readily readable.

Another object of the invention is the provision of a novel composite drafting ruler or scale, com-- prising a metal or like body provided with an edge strip or strips made -of a plastic molded thereon and mechanically interlocked therewith in such a manner as to be rmly and non-removably secured to the body.

Another object of the invention is the provision of a novel method of making a composite draftling ruler or scale, comprising a metal or like body. having plastic edge strips mechanically interlocked therewith, wherein the edge strips are preformed to approximately their final shape and subsequently assembled with thepreviously lformed body and molded thereto by heat and pressure The present invention resides in certain details of construction, combinations and arrangements of parts and further objects and advantages thereof will be apparent to those skilled in the art to -which it relates from the following description which,

Fig. 1 is a plan view of adrafting ruler or scale embodying the present invention.

Fig. 1.

Fig. 3 is an enlarged section-onthe line 3-3 of Fig. 2 is an enlarged section on the line 2-12 ofl Fig. 1 with portions in elevation.

Fig. 4'is anenlargedsectionlon the line 4 4 of Hg. 1.v

mg. 5 is m expended view or the nner shown amoditled construction.

Fig. 'I is a front elevation of a portion of a pair of molds for preforming the plastic edge strip.

the molds closed. Fig. is an enlarged plan of a portion of the preformed body of the ruler before the edge strips are assembled therewith.

` Fig. 11 is a section on the line Ii-li of Fig. 10.

' Fig. 12 is an enlarged plan of a portion of the preformed edge strip of the ruler before the 6 same isv assembled with the body portion of the ruler.

Fig. 13 isa sectionon the line I3-I3 of Fig. 12. Fig. 14 is a front elevation, with portions in section on the line |4-I4 of Fig. 15, ofva portion 10 of a pair of molds for molding the edge strip, etc. to the body portion and to each other, showing the various parts of the ruler in thedie cavity and the punch raised.

. Fig. 15 is an enlarged section on the line l5-I5 15 of Fig. 14, and v Fig. 16 is a view similar to Fig. 15 the molds closed.

Referring to Figs. 1 to 5 inclusive of the drawings, the drafting ruler or scale shown therein is 20 especially adapted for use with drafting machines such as shown in either of my United States Patents No. 1,909,289 or No. 1,909,291. Generally speaking, the ruler comprises a metal or like stiliening body A and plastic edge strips B, preferably made of a polymerization product of a vinyl compound, molded thereto and mechanically interlocked therewith. In the preferred embodiment shown the ends of the ruler are also provided with end strips C of the plastic, in such a manner that the edges of the ruler are formed entirely of the plastic. The side edges 'of the ruler are beveled, as clearly shown in Figs. 2 and 3, and provided with graduations, etc., preferably molded therein- Ollposlte ends of the ruler are provided with chuck plates i0, adjustably secured to the body portion A as by screws Il. The two chuck plates permit the ruler to be reversed. that is, either end of the ruler may be chucked to the chuck arm of the drafting machine, as is 40 the usual custom. The chucks and chuck arm,

. as well as the body portion A of the ruler, are

' preferably made of Duralu'min and given an oxide coating by an electrolytic process known in the Aart which produces a surface that is free from glare, has a pleasing appearance, and will not rub off and soil the drawing paper or surface upon which the ruler is'used. 4

We have discovered that the polymerization products of vinyl compounds, such as vinyl chloride, vinyl acetate or vinyl benzine have characteristics which adapt them peculiarly to the present use. Plastics made of these'products are light in weight, tough, and flexible without being brittle, feel well to the touch, and can be tinted varbut showing ious colors. Edge strips made therefrom do not shrink orvwarp, are light in weight, durable, easy to clean', etc. The vinyl acetate is permanently nearly white and can be readily made transparent, in which event the graduations may be placed on the underside of the edge strip. Commercially known plastics sold under the trade names Vinolyte, Vietro, Galva, etc., are suitable for the present purpose. These products are polymerization products of vinyl compounds, can be molded at relatively low temperatures and pressures, and have a very low and constant mold shrinkage, which latter characteristic makes it possible to mold graduations on the edge strips very accurately. Graduatlons may also be readily cut therein, but it is usually less expensive to mold the same.

The side edges i2 of the body A are top bevel to conform somewhat to the shape of the finished ruler and both sides are undercut or reduced in thickness' so that the plastic edge strips, which in the present instance form the entire beveled surface of the ruler, will come flush with the suriace of the body between the edge strips. The upper surface of each of the side edges is provided with a dove-tailed or undercut groove id into which portions of the plastic flows during molding to securely lock the upper prongs i5 of the V-shaped edge strips to the upper side of the top bevel of the body A. The lower undercut edges of the body A are also provided with grooves I6, the outer sides Il of which, at least, are undercut and into which the plastic hows during the molding operation to securely lock the lower prongs i8 of the edge strips to the body.

`As shown, both ends of the body portion .d are grooved as at i9 to provide upper and lower flanges and 2i, respectively, and the plastic which extends-across the ends of' the ruler pro jects as at 22, see Fig. Liuto the groove i@ formed between said ilanges. This construction produces a very strong connection between the various parts. 'If desired, the upper and lower exposed metal surfaces of the body A may likewise be covered with the plastic. in this event the metal body portion is preferably made of reduced thickness insidev of the edge strips and the metal removed replaced by plastic material bonded to both the body and the edge strips. Such a construction is illustrated in Fig. 6, wherein the body'A' is similar to the body A previously referred to, except for the fact that a small amount of metal has been removed from -both the upper and lower surfaces thereof between the edge strips B `and replaced by the plastic as at 23 and 24, respectively.

In order to get an even distribution of the -plastic along the edges of the ruler and thereby avoid the possibility of setting up undesirable and detrimental strains inthe edge strips, the edge strips B are preferably preformed to apl proximately their `inal shape and subsequently assembled with the body portion preparatory to thermal-molding operation. While the` end strips-,C maybe formed in any desired manner,

preferably, they are also preformed to substantially their finished shape and bonded with the bodyA .and the edge strips B vduring the final vmolding operation. In the modification shown in Fig. 6 the plastic parts 23 and 24 are preferably-preformed, or consist of sheet material Vbonded to the edge strips and the body in the in which form they are' very dense, hard, and tough. These desirable characteristics are in part lost in the event the material is greatly disturbed in subsequent molding operations, and the method of the present invention contemplates the formation of edge strips from this sheet material with the minimum disturbance or re-distribution of the material, especially that part of the material which in subsequent use is subject to the greatest wear. The preferred manner of carrying out the method of the present invention is shown in Figs. 7 to 16 inclusive. As previously stated the method of this invention consists in preforming the body portion A to substantially their iinal finished shape, and the edge strips B to approximately their final finished shape, assembling the various parts together, and bonding the same together under heat and pressure.

The edge strips B are preferably preformed to the shape shown in Figs. 12 and 13 by cooperating molds consisting of a punch 25 and a die 26, from commercial material in sheet form oi desired thickness cut to appropriate length, with a minimum disturbance or redistribution of the sheet material especially that part of the material which ultimately forms the ruling edge and the top and bottom surfaces of the edge strip. The sheet material 2i is placed in the die cavities 28 in the manner shown in Fig. 8, and upon the initial lowering of the punch ,25 the lower edges of the sheets 2i are forced down into the bottom of the cavities with substantially no dis-I turbance or ree-distribution of that part of the material which forms the ruling edge of the edge strips. Upon continued movement of the punch the upper parts of the sheets 21 fill the upper cavities of the die and punch, and undergo considerable change, but this isvnot materially detri mental to the iinished product, since these parts of the edge strip are not subject to the same wear, etc., as the ruling edges.

The cross section of the finished edge strip blanks 2i as shown in Fig.` 13 is il-shaped, with the right hand prong extended. Recesses 30 in the punch 25 form rectangular projections 3i on the inside of the upper ends of the extended legs 32, and smaller apertures 33 in the die 26 form small projections 34 on the corresponding sides of the other legs 35 of the blanks. The blanks 2S are removed from the punch by placing a tool under the upper outside edge thereof and bending the extended prong outwardly. When the edge strip blanks 29 are assembled with the body A, the projections 3l extend into the grooves i4 and the projections 34 come opposite the grooves '16. The projections 3i are higher than the grooves M are deep so as to provide the necessary material for filling the dovetails. The material for filling the grooves I6 comes from the projectionsl 34.r

The nal molding operation is performed in the molds shown in Figs. 14, 15 and 16, comprisinge. punch 40 which cooperates with the die 4i to formpthe cavity. The manner in which-the preformed parts of the ruler are assembled in the die 4l is clearly shown in Figs. 14 and 15. 'I'he closedposition of the molds is shown in Fig. 16. The body portion A is held from moving lengthwise by alpin 42 extending into the mold cavity and projecting into one of the apertures 43 in the body subsequently used in attaching the chuck platesll). Both molding operations herein referred to take place under heat and pressure, and it is to, be understood that adel cally produced oxide coating. on the exposed portions oi' said metal ruler body.

quate means (not shown) is provided for heating the molds and forcing the same together.

From the foregoing description of the preferred embodiment of the invention and the preferred method-of forming the same, it will be apparent that the objects heretofore enumerated have been accomplished. While the preferred embodiment and the preferred method of making the same have been herein described in considerable de-v taill we do not wish to be limited to the construction or steps shown, which may be varied within the scope of this invention and we particularly point out and claim as our invention the following:

1. A composite drafting ruler comprising a metal ruler body made of an aluminum alloy and extending from the upper side of the ruler proper to the lower side thereof, the perimeter of the lower side of said ruler proper being formed of plastic molded in position and mechanically interlocked with the ruler body. and an electrolyti- 2. A compomte drafting rulercomprising a y metal ruler body made of an aluminum' alloy and extending from the upper side of the ruler proper to the lower side thereof. said ruler body having outwardly tapering top bevel edge portions, V- shaped edge stripsenssing around said bevel edge portions of saidvruler body, end strips ccnnected to the ends of said edge strips and extending across the ends of said ruler body, said edge strips and said end strips being formed of a plastic molded in position, said bevel edge portions and said edge strips having interfltting tongues and grooves for. mechanically interlocking said edge strips to said edge portions. and an electrolytically produced oxide coating on the exposed portions of said metal ruler 

